Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 5 - Solving Systems of Linear Equations - Chapter Review - Page 283: 10

Answer

The solution is $(4,5)$.

Work Step by Step

The given system of equations is $8x-7y=-3$ ...... (1) $6x-5y=-1$ ...... (2) Multiply equation (1) by $-3$. $\Rightarrow -3(8x-7y)=-3(-3)$ Use distributive property. $\Rightarrow -24x+21y=9$ ...... (3) Multiply equation (2) by $4$. $\Rightarrow 4(6x-5y)=4(-1)$ Use distributive property. $\Rightarrow 24x-20y=-4$ ...... (4) Add equation (3) and (4). $\Rightarrow -24x+21y+24x-20y=9-4$ Add like terms. $\Rightarrow y=5$ Substitute $5$ for $y$ in equation (2). $\Rightarrow 6x-5(5)=-1$ Simplify. $\Rightarrow 6x-25=-1$ Add $25$ to each side. $\Rightarrow 6x-25+25=-1+25$ Simplify. $\Rightarrow 6x=24$ Divide each side by $6$. $\Rightarrow \frac{6x}{6}=\frac{24}{6}$ Simplify. $\Rightarrow x=4$ Check $(x,y)=(4,5)$ Equation (1): $\Rightarrow 8x-7y=-3$ $\Rightarrow 8(4)-7(5)=-3$ $\Rightarrow 32-35=-3$ $\Rightarrow -3=-3$ True. Equation (2): $\Rightarrow 6x-5y=-1$ $\Rightarrow 6(4)-5(5)=-1$ $\Rightarrow 24-25=-1$ $\Rightarrow -1=-1$ True. Hence, the solution is $(4,5)$.
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